DESCRIPTION: Household consumption of energy for space heating and cooling, lighting, appliances, transportation, and other energy services is a key driver of national energy demand, and of energy-related environmental issues such as acid rain, local air pollution, and climate change. Changes in population age structure may have potentially important direct or indirect influences on energy demand, particularly through the loss of household economies of scale as aging drives a decrease in average household size. The proposed research aims to improve the treatment of demographic factors in medium-to long-term energy and emissions projections by incorporating age structure effects. Household survey data from the United States will be used to test the hypotheses that direct and indirect effects of aging have a substantial impact on per capita residential energy consumption, independent of other factors such as income, urban/rural status, and physical size of the housing unit. The study will draw on results of the Residential Energy Consumption Survey to examine cross-sectional data, use time series data to evaluate the contribution of aging to changes in energy consumption over the past several decades, and develop relationships between age-related and energy variables that can be used to estimate the potential contribution of aging to future consumption.